Composite pavement structures

ABSTRACT

A composite pavement structure comprises a wearing course layer and a base course layer disposed below the wearing course layer. The wearing course layer comprises aggregate, e.g. glass and rock, and an elastomeric composition. The elastomeric composition comprises the reaction product of an isocyanate component and an isocyanate-reactive component. The isocyanate component comprises a polymeric isocyanate, and optionally, an isocyanate-prepolymer. The isocyanate-reactive component comprises a hydrophobic polyol and a chain extender having at least two hydroxyl groups and a molecular weight of from about 62 to about 220. The chain extender is present in the isocyanate-reactive component in an amount of from about 1 to about 20 parts by weight based on 100 parts by weight of the isocyanate-reactive component. The base course layer comprises aggregate which is the same or different than the aggregate of the wearing course layer. Methods of forming the composite pavement structure are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/517,928, filed on Sep. 10, 2012, which is the National Stage ofInternational Patent Application No. PCT/US2010/061587, filed on Dec.21, 2010, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/288,637, filed on Dec. 21, 2009, the contents ofwhich are incorporated herewith by reference in their entirety.

FIELD OF THE INVENTION

The present invention generally relates to a composite pavementstructure comprising a wearing course layer comprising aggregate and anelastomeric composition, and more specifically to a composite pavementstructure comprising a base course layer and a wearing course layercomprising aggregate comprising glass and an elastomeric compositioncomprising an isocyanate component comprising a polymeric isocyanate,and optionally, an isocyanate prepolymer, and the elastomericcomposition further comprising an isocyanate-reactive componentcomprising a hydrophobic polyol and a chain extender, and to methods offorming the composite pavement structure.

DESCRIPTION OF THE RELATED ART

The use of composite materials to form articles such as pavement isgenerally known in the construction art. Generally, the compositematerial is produced by mixing at least one aggregate and at least onebinder composition together. For example, in the case of concrete, theaggregate comprises sand and gravel, and the binder compositioncomprises cement and water.

Recently, there have been advancements in the use of polymeric materialsas binder compositions. Generally, once the aggregate and the bindercomposition are mixed together, the composite material remains pliableor “workable” for only a short time, e.g. 45 minutes, before thecomposite material cures and is no longer pliable. Therefore, suchcomposite materials are typically produced onsite as opposed to offsiteto increase working time. Offsite production requires the compositematerial to be transported to a construction site thereby furtherdecreasing working time of the composite material once onsite.

Conventional methods of producing composite materials onsite requireaggregate to be placed on the ground (or already be present on theground) before coming into contact with the binder composition.Subsequently, the aggregate is sprayed (or sheeted) with the bindercomposition. A significant drawback of such a method is an inconsistentcoating of the aggregate, which creates inconsistencies in the compositematerial. Inconsistencies in the composite material can result in earlyfailure of the composite material thereby requiring the compositematerial to be replaced at additional cost. In addition, such methodsare time consuming. A common form of failure of the composite materialis spalling, where the aggregate loosens from the composite material,eventually dislodging from the composite material altogether.

Alternatively, the aggregate and binder composition are tumbled in abatch mixer for several minutes until the aggregate is uniformly coatedwith the binder composition before it is set into place, such as bypouring the composite material into place. A significant drawback ofthis process, commonly referred to as a batch process, is once againreduced working time since the binder composition begins to immediatelycure once present in the batch mixer.

Accordingly, there remains an opportunity to provide an improvedpavement structures. There also remains an opportunity for improvedmethods of forming pavement structures.

SUMMARY OF THE INVENTION AND ADVANTAGES

The present invention provides a composite pavement structure. Thecomposite pavement structure comprises a wearing course layer and a basecourse layer disposed below the wearing course layer. The wearing courselayer comprises aggregate and an elastomeric composition. The aggregateof the wearing course layer comprises glass and, optionally, rock. Theelastomeric composition comprises the reaction product of an isocyanatecomponent and an isocyanate-reactive component. The isocyanate componentcomprises a polymeric isocyanate, and optionally, anisocyanate-prepolymer. The isocyanate-reactive component comprises ahydrophobic polyol and a chain extender having at least two hydroxylgroups and a molecular weight of from about 62 to about 220. The chainextender is present in the isocyanate-reactive component in an amount offrom about 1 to about 20 parts by weight based on 100 parts by weight ofthe isocyanate-reactive component. The base course layer also comprisesaggregate, which can be the same as or different than the aggregate ofthe wearing course layer. The present invention further provides amethod of forming the composite pavement structure.

The elastomeric composition has excellent physical properties that areimparted to the wearing course layer, such as improved bond strengthbetween the elastomeric composition and the aggregate, improvedcompressive strength, improved shear strength, and improved flexuralstrength, which reduces spalling of the aggregate from the wearingcourse layer. The composite pavement structure can be either nonporousor porous, thereby reducing water run-off and other problems associatedwith conventional pavement and similar structures.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated,as the same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a partial cross-sectional view of a composite pavementstructure illustrating water migration through the composite pavementstructure, the composite pavement structure includes a base course layerand a wearing course layer formed from composite material;

FIG. 2 is a partial cross-sectional view of another composite pavementstructure illustrating water migration through the composite pavementstructure, the composite pavement structure further includes a chokercourse layer;

FIG. 3 is a partial cross-sectional view of another composite pavementstructure illustrating water migration through the composite pavementstructure, the composite pavement structure further includes ageosynthetic;

FIG. 4 is an enlarged view depicting a porous embodiment of thecomposite material;

FIG. 5 is an enlarged view depicting a nonporous embodiment of thecomposite material;

FIG. 6 is a bar graph illustrating crush strength results betweenuntreated and treated aggregate; and

FIG. 7 is a plot illustrating Dynamic Mechanical Analysis (DMA) resultsof a composite material.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a composite pavement structure and amethod of forming the composite pavement structure, both of which aredescribed further below. The present invention also provides a systemfor forming an elastomeric composition which bonds aggregate. The systemis described immediately hereafter.

The system comprises an isocyanate component and an isocyanate-reactivecomponent. In certain embodiments, the isocyanate component comprises apolymeric isocyanate, and optionally, an isocyanate-prepolymer. In otherembodiments, the isocyanate component comprises the polymeric isocyanateand the isocyanate-prepolymer. The isocyanate-reactive componentcomprises a hydrophobic polyol and a chain extender. Typically, thesystem is provided in two or more discrete components, such as theisocyanate component and the isocyanate-reactive (or resin) component,i.e., as a two-component (or 2K) system, which is described furtherbelow.

It is to be appreciated that reference to the isocyanate and resincomponents, as used herein, is merely for purposes of establishing apoint of reference for placement of the individual components of thesystem, and for establishing a parts by weight basis. As such, it shouldnot be construed as limiting the present invention to only a 2K system.For example, the individual components of the system can all be keptdistinct from each other. The terminology “isocyanate-reactive”component and “resin” component is interchangeable in the description ofthe present invention.

The system may also comprise additional components, which may beincluded with either one or both of the isocyanate and resin components,or completely distinct, such as in a third component, as describedfurther below. The system is used to form the elastomeric composition.In certain embodiments, the elastomeric composition is the reactionproduct of the isocyanate and isocyanate-reactive components. Theelastomeric composition is described further below.

If employed, the isocyanate-prepolymer is generally the reaction productof an isocyanate and a polyol and/or a polyamine, typically the reactionproduct of an isocyanate and a polyol. The isocyanate-prepolymer can beformed by various methods understood by those skilled in the art or canbe obtained commercially from a manufacturer, a supplier, etc.

With regard to the isocyanate used to form the isocyanate-prepolymer,the isocyanate includes one or more isocyanate (NCO) functional groups,typically at least two NCO functional groups. Suitable isocyanates, forpurposes of the present invention include, but are not limited to,conventional aliphatic, cycloaliphatic, aryl and aromatic isocyanates.In certain embodiments, the isocyanate is selected from the group ofdiphenylmethane diisocyanates (MDIs), polymeric diphenylmethanediisocyanates (PMDIs), and combinations thereof. Polymericdiphenylmethane diisocyanates are also referred to in the art aspolymethylene polyphenylene polyisocyanates. Examples of other suitableisocyanates, for purposes of the present invention include, but are notlimited to, toluene diisocyanates (TDIs), hexamethylene diisocyanates(HDIs), isophorone diisocyanates (IPDIs), naphthalene diisocyanates(NDIs), and combinations thereof. Typically, the isocyanate used to formthe isocyanate-prepolymer comprises diphenylmethane diisocyanate (MDI).

If employed to form the isocyanate-prepolymer, the polyol includes oneor more hydroxyl (OH) functional groups, typically at least two OHfunctional groups. The polyol can be any type of polyol known in theart. The polyol is typically selected from the group of ethylene glycol,diethylene glycol, propylene glycol, dipropylene glycol, butanediol,glycerol, trimethylolpropane, triethanolamine, pentaerythritol,sorbitol, and combinations thereof. Other suitable polyols, for purposesof the present invention, are described below with description of anadditional, optional, component, a supplemental polyol.

The polyol can be used in various amounts relative to the isocyanate, aslong as an excess of NCO functional groups relative to OH functionalgroups are present prior to reaction such that theisocyanate-prepolymer, after formation, includes NCO functional groupsfor subsequent reaction. The isocyanate-prepolymer typically has an NCOcontent of from about 18 to about 28, more typically from about 20 toabout 25, and yet more typically about 22.9, wt. %.

If employed to form the isocyanate-prepolymer, the polyamine includesone or more amine functional groups, typically at least two aminefunctional groups. The polyamine can be any type of polyamine known inthe art. The polyamine is typically selected from the group of ethylenediamine, toluene diamine, diaminodiphenylmethane and polymethylenepolyphenylene polyamines, aminoalcohols, and combinations thereof.Examples of suitable aminoalcohols include ethanolamine, diethanolamine,triethanolamine, and combinations thereof.

The polyamine can be used in various amounts relative to the isocyanate,as long as an excess of NCO functional groups relative to aminefunctional groups are present prior to reaction such that theisocyanate-prepolymer, after formation, includes NCO functional groupsfor subsequent reaction. The NCO content of the isocyanate-prepolymer isas described and exemplified above.

It is to be appreciated that the isocyanate-prepolymer may be formedfrom a combination of two or more of the aforementioned polyols and/ortwo or more of the aforementioned polyamines. Typically, theisocyanate-prepolymer is a reaction product of the isocyanate and atleast one polyol such that the isocyanate-prepolymer includes urethanelinkages and NCO functional groups after formation. In a specificembodiment of the present invention, the isocyanate-prepolymer comprisesa blend of polymeric methyldiphenyldiisocyanate and quasi-prepolymers of4,4′-methyldiphenyldiisocyanate. Specific examples of suitableisocyanate-prepolymers, for purposes of the present invention, arecommercially available from BASF Corporation of Florham Park, N.J.,under the trademark LUPRANATE®, such as LUPRANATE® MP102. It is to beappreciated that the system can include a combination of two or more ofthe aforementioned isocyanate-prepolymers.

With regard to the polymeric isocyanate, the polymeric isocyanateincludes two or more NCO functional groups. The polymeric isocyanatetypically has an average functionality of from about 1.5 to about 3.0,more typically from about 2.0 to about 2.8, and yet more typically about2.7. The polymeric isocyanate typically has an NCO content of from about30 to about 33, more typically from about 30.5 to about 32.5, and yetmore typically about 31.5, wt. %.

Suitable polymeric isocyanates, for purposes of the present inventioninclude, but are not limited to, the isocyanates described andexemplified above for description of the isocyanate-prepolymer.Typically, the polymeric isocyanate comprises polymeric diphenylmethanediisocyanate (PMDI).

Specific examples of suitable polymeric isocyanates, for purposes of thepresent invention, are commercially available from BASF Corporationunder the trademark LUPRANATE®, such as LUPRANATE® M20 Isocyanate. It isto be appreciated that the system can include a combination of two ormore of the aforementioned polymeric isocyanates.

The isocyanate-prepolymer is typically present in the isocyanatecomponent in an amount of from about 25 to about 75, more typically fromabout 50 to about 75, yet more typically from about 55 to about 65, andyet even more typically about 60, parts by weight, each based on 100parts by weight of the isocyanate component. In certain embodiments, theisocyanate-prepolymer is typically present in the system in an amount offrom about 50 to about 250, more typically from about 100 to about 200,yet more typically from about 125 to about 175, and yet even moretypically about 150, parts by weight, each per 100 parts by weight ofthe polymeric isocyanate in the system. Said another way, theisocyanate-prepolymer and the polymeric isocyanate are typically presentin the system, e.g. in the isocyanate component, in a weight ratio offrom about 1:2 to about 2.5:1, more typically from about 1:1 to about2:1, yet more typically from about 1.25:1 to 1.75:1, and yet even moretypically about 1.5:1.

Without being bound or limited to any particular theory, it is believedthat the combination and ratios of the isocyanate-prepolymer and thepolymeric isocyanate, as described and exemplified immediately above,imparts the elastomeric composition with increased tensile strength,elongation, hardness, and glass transition temperature, as well asimproved tear strength relative to conventional elastomericcompositions.

With regard to the hydrophobic polyol, the hydrophobic polyol includesone or more OH functional groups, typically at least two OH functionalgroups. Hydrophobicity of the hydrophobic polyol can be determined byvarious methods, such as by visual inspection of the reaction product ofthe hydrophobic polyol with isocyanate where the reaction product hasbeen immediately de-gassed after mixing the two components and thenintroduced into water, where the reaction product is allowed to cure. Ifthere is no evidence of marring or wrinkling at the interface (orsurface) between the reaction product and the water, or if there is noevidence of bubble or foam formation, hydrophobicity of the hydrophobicpolyol is considered excellent.

The hydrophobic polyol typically comprises a natural oil polyol (NOP).In other words, the hydrophobic polyol is typically not apetroleum-based polyol, i.e., a polyol derived from petroleum productsand/or petroleum by-products. In general, there are only a few naturallyoccurring vegetable oils that contain unreacted OH functional groups,and castor oil is typically the only commercially available NOP produceddirectly from a plant source that has sufficient OH functional groupcontent to make castor oil suitable for direct use as a polyol inurethane chemistry. Most, if not all, other NOPs require chemicalmodification of the oils directly available from plants. The NOP istypically derived from any natural oil known in the art, typicallyderived from a vegetable or nut oil. Examples of suitable natural oils,for purposes of the present invention, include castor oil, and NOPsderived from soybean oil, rapeseed oil, coconut oil, peanut oil, canolaoil, etc. Employing natural oils can be useful for reducingenvironmental footprints.

Typically, as alluded to above, the hydrophobic polyol comprises castoroil. Those skilled in the art appreciate that castor oil inherentlyincludes OH functional groups whereas other NOPs may require one or moreadditional processing steps to obtain OH functional groups. Suchprocessing steps, if necessary, are understood by those skilled in theart. Suitable grades of castor oil, for purposes of the presentinvention, are commercially available from a variety of suppliers. Forexample, T31® Castor Oil, from Eagle Specialty Products (ESP) Inc. ofSt. Louis, Mo., can be employed as the hydrophobic polyol. Specificexamples of other suitable hydrophobic polyols, for purposes of thepresent invention, are commercially available from Cognis Corporation ofCincinnati, Ohio, under the trademark SOVERMOL®, such as SOVERMOL® 750,SOVERMOL® 805, SOVERMOL® 1005, SOVERMOL® 1080, and SOVERMOL® 1102.

The hydrophobic polyol is typically present in the system in an amountof from about 80 to about 99, more typically about 85 to about 95, yetmore typically from about 90 to about 95, and yet even more typicallyabout 92.5, parts by weight, each based on 100 parts by weight of theresin component of the system. It is to be appreciated that the systemcan include a combination of two or more of the aforementionedhydrophobic polyols.

With regard to the chain extender, the chain extender has at least twoOH functional groups. The chain extender typically has a molecularweight of from about 62 to about 220, more typically from about 62 toabout 150, and yet more typically about 132. As such, the chain extendercan be referred to in the art as a “short” chain extender. The chainextender typically comprises an alkylene glycol. Examples of suitablechain extenders, for purposes of the present invention, includedipropylene glycol (DPG), diethylene glycol (DEG), NIAX® DP-1022,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and2-butene-1,4-diol. In a specific embodiment, the chain extender isdipropylene glycol.

The chain extender is typically present in the system in an amount offrom about 1.0 to about 20, more typically from about 5.0 to about 10,and yet more typically about 7, parts by weight, each based on 100 partsby weight of the resin component. It is to be appreciated that thesystem may include any combination of two or more of the aforementionedchain extenders.

Without being bound or limited to any particular theory, it is believedthat the chain extender imparts increased strength to the elastomericcomposition, as well as increased strength, tear strength, and hardnessto the elastomeric composition.

In other embodiments of the present invention, a supplemental polyol,such as a petroleum-based polyol, may be used in addition to thehydrophobic polyol. If employed, the supplemental polyol is typicallyselected from the group of conventional polyols, such as ethyleneglycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, glycerol, trimethylolpropane, triethanolamine, pentaerythritol,sorbitol, and combinations thereof. Typically, the supplemental polyolis selected from the group of polyether polyols, polyester polyols,polyether/ester polyols, and combinations thereof however, othersupplemental polyols may also be employed as described further below.

Suitable polyether polyols, for purposes of the present inventioninclude, but are not limited to, products obtained by the polymerizationof a cyclic oxide, for example ethylene oxide (EO), propylene oxide(PO), butylene oxide (BO), or tetrahydrofuran in the presence ofpolyfunctional initiators. Suitable initiator compounds contain aplurality of active hydrogen atoms, and include water, butanediol,ethylene glycol, propylene glycol (PG), diethylene glycol, triethyleneglycol, dipropylene glycol, ethanolamine, diethanolamine,triethanolamine, toluene diamine, diethyl toluene diamine, phenyldiamine, diphenylmethane diamine, ethylene diamine, cyclohexane diamine,cyclohexane dimethanol, resorcinol, bisphenol A, glycerol,trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, and combinationsthereof.

Other suitable polyether polyols include polyether diols and triols,such as polyoxypropylene diols and triols andpoly(oxyethylene-oxypropylene)diols and triols obtained by thesimultaneous or sequential addition of ethylene and propylene oxides todi- or trifunctional initiators. Copolymers having oxyethylene contentsof from about 5 to about 90% by weight, based on the weight of thepolyol component, of which the polyols may be block copolymers,random/block copolymers or random copolymers, can also be used. Yetother suitable polyether polyols include polytetramethylene glycolsobtained by the polymerization of tetrahydrofuran.

Suitable polyester polyols, for purposes of the present inventioninclude, but are not limited to, hydroxyl-terminated reaction productsof polyhydric alcohols, such as ethylene glycol, propylene glycol,diethylene glycol, 1,4-butanediol, neopentylglycol, 1,6-hexanediol,cyclohexane dimethanol, glycerol, trimethylolpropane, pentaerythritol orpolyether polyols or mixtures of such polyhydric alcohols, andpolycarboxylic acids, especially dicarboxylic acids or theirester-forming derivatives, for example succinic, glutaric and adipicacids or their dimethyl esters sebacic acid, phthalic anhydride,tetrachlorophthalic anhydride or dimethyl terephthalate or mixturesthereof. Polyester polyols obtained by the polymerization of lactones,e.g. caprolactone, in conjunction with a polyol, or of hydroxycarboxylic acids, e.g. hydroxy caproic acid, may also be used.

Suitable polyesteramides polyols, for purposes of the present invention,may be obtained by the inclusion of aminoalcohols such as ethanolaminein polyesterification mixtures. Suitable polythioether polyols, forpurposes of the present invention, include products obtained bycondensing thiodiglycol either alone, or with other glycols, alkyleneoxides, dicarboxylic acids, formaldehyde, aminoalcohols oraminocarboxylic acids. Suitable polycarbonate polyols, for purposes ofthe present invention, include products obtained by reacting diols suchas 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol ortetraethylene glycol with diaryl carbonates, e.g. diphenyl carbonate, orwith phosgene. Suitable polyacetal polyols, for purposes of the presentinvention, include those prepared by reacting glycols such as diethyleneglycol, triethylene glycol or hexanediol with formaldehyde. Othersuitable polyacetal polyols may also be prepared by polymerizing cyclicacetals. Suitable polyolefin polyols, for purposes of the presentinvention, include hydroxy-terminated butadiene homo- and copolymers andsuitable polysiloxane polyols include polydimethylsiloxane diols andtriols.

Specific examples of suitable supplemental polyols, for purposes of thepresent invention, are commercially available from BASF Corporationunder the trademark of PLURACOL®, such as PLURACOL® GP Series polyols. Aspecific example of a suitable supplement polyol, for purposes of thepresent invention, is PLURACOL® GP430.

If employed, the supplemental polyol is typically present in the systemin an amount of from about 1 to about 75, more typically from about 10to about 50, and yet more typically about 40, parts by weight, eachbased on 100 parts by weight of the resin component of the system. It isto be appreciated that the system may include any combination of two ormore of the aforementioned supplemental polyols.

The system may include one or more additional components, such as anadditive component, in addition or alternate to the supplemental polyol.The additive component may comprise any conventional additive known inthe art. Suitable additives, for purposes of the present inventioninclude, but are not limited to, chain-extenders, cross-linkers,chain-terminators, processing additives, adhesion promoters, flameretardants, anti-oxidants, defoamers, anti-foaming agents, waterscavengers, molecular sieves, fumed silicas, ultraviolet lightstabilizers, fillers, thixotropic agents, silicones, surfactants,catalysts, colorants, inert diluents, and combinations thereof. Ifemployed, the additive component may be included in the system anyamount, such as from about 0.05 to 10 parts by weight based on 100 partsby weight of the resin component of the system.

In certain embodiments, the additive component comprises an antifoamingagent. In one embodiment, the antifoaming agent comprises a siliconefluid including powdered silica dispersed therein. The silicone fluidcan be employed to reduce and/or eliminate foaming of the elastomericcomposition. It should be appreciated that the silicone fluid may bepredisposed in a solvent. Examples of antifoaming agents includeAntifoam MSA and Antifoam A, commercially available from Dow Corning ofMidland, Mich.

If employed, the antifoaming agent is typically present in the system inan amount of from about 0.01 to about 0.10, more typically from about0.025 to about 0.075, and yet more typically about 0.05, parts byweight, each based on 100 parts by weight of the resin component of thesystem. It is to be appreciated that the system may include anycombination of two or more of the aforementioned antifoaming agents.

In certain embodiments, the additive component comprises a molecularsieve. The molecular sieve is a hygroscopic agent that can be employedto maintain or increase desiccation, i.e., a state of dryness. Themolecular sieve typically comprises molecules having a plethora of smallpores. The small pores allow for molecules having a size smaller thanthe pores, such as water molecules, to be adsorbed while largermolecules, such as those present in the isocyanate and resin component,cannot be adsorbed. Typically, the molecular sieve can adsorb water upto and in excess of 20% of the weight of the molecular sieve. Themolecular sieve, therefore, can act synergistically and in concert withthe hydrophobic polyol to minimize the effect of water on theelastomeric composition by adsorbing water before the water has a chanceto react with the isocyanate component of the system.

If employed, it should be appreciated that any molecular sieve known inthe art can be used, such as aluminosilicate minerals, clays, porousglasses, microporous charcoals, zeolites, active carbons, or syntheticcompounds that have open structures through which small molecules, e.g.water, can diffuse. Examples of suitable molecular sieves includeBaylith Paste and Molecular Sieve 3A, which are available from a varietyof suppliers, such as Zeochem of Louisville, Ky.

If employed, the molecular sieve is typically present in the system inan amount of from about 0.01 to about 5.0, more typically from about0.10 to about 2.0, and yet more typically about 0.50, parts by weight,each based on 100 parts by weight of the resin component of the system.It is to be appreciated that the system may include any combination oftwo or more of the aforementioned molecular sieves.

In certain embodiments, the additive component comprises fumed silica,which is available from a variety of suppliers. An example of a suitablefumed silica is AEROSIL® R-972, commercially available from EvonicIndustries Inc. of Essen, Germany. Fumed silica generally acts as arheology control agent, and, if the fumed silica is hydrophobic, itimparts additional hydrophobicity to the elastomeric composition.

If employed, the fumed silica is typically present in the system in anamount of from about 0.10 to about 10.0, more typically from about 1.0to about 7.0, and yet more typically about 5.0, parts by weight, eachbased on 100 parts by weight of the resin component of the system. It isto be appreciated that the system may include any combination of two ormore fumed silicas.

In certain embodiments, the additive component comprises a colorant. Thecolorant can be selected from the group of pigments, dyes, andcombinations thereof. The colorant can be in either liquid or powderform. If employed, the colorant is typically a pigment or a pigmentblend of two or more pigments. The pigment, or pigment blend, is used toimpart a desired color to the elastomeric composition and, if thepigment is inorganic, the pigment can also impart UV protection to theelastomeric composition.

Different types of pigments can be used for purposes of the presentinvention. For example, titanium dioxide can be used to impart a whitecolor and carbon black can be used to impart a black color, to theelastomeric composition, respectively, while various blends of titaniumdioxide and carbon black can be used to impart various shades of gray tothe elastomeric composition.

Examples of suitable grades of carbon black and titanium dioxide forpurposes of the present invention are commercially available fromColumbian Chemicals Company of Marietta, Ga., and DuPont® TitaniumTechnologies of Wilmington, Del., respectively. Other pigmentsincluding, but not limited to, red, green, blue, yellow, green, andbrown, and pigment blends thereof, can also be used to impart color tothe elastomeric composition in addition to or alternative to carbonblack and/or titanium dioxide.

More specific examples of colors, based on one or more colorants,include sapphire blue, jade green, Sedona red, amber brown, and topazbrown. Examples of suitable grades of pigments for purposes of thepresent invention are commercially available from various companies suchas BASF Corporation and Penn Color, Inc. of Hatfield, Pa. It is to beappreciated that various blends of the aforementioned colorants, e.g.pigments, can be used to impart the elastomeric composition with variouscolors, strengths, and shades.

If employed, the colorant is typically present in the system in anamount of from about 0.10 to about 5.0, more typically from about 1.0 toabout 3.0, and yet more typically about 2.0, parts by weight, each based100 parts by weight of the resin component of the system. It is to beappreciated that the system may include any combination of two or moreof the aforementioned colorants.

In certain embodiments, the additive component comprises a catalystcomponent. In one embodiment, the catalyst component comprises a tincatalyst. Suitable tin catalysts, for purposes of the present invention,include tin(II) salts of organic carboxylic acids, e.g. tin(II) acetate,tin(II) octoate, tin(II) ethylhexanoate and tin(II) laurate. In oneembodiment, the organometallic catalyst comprises dibutyltin dilaurate,which is a dialkyltin(IV) salt of an organic carboxylic acid. Specificexamples of suitable organometallic catalyst, e.g. dibutyltindilaurates, for purposes of the present invention, are commerciallyavailable from Air Products and Chemicals, Inc. of Allentown, Pa., underthe trade name DABCO®. The organometallic catalyst can also compriseother dialkyltin(IV) salts of organic carboxylic acids, such asdibutyltin diacetate, dibutyltin maleate and dioctyltin diacetate.

Examples of other suitable catalysts, for purposes of the presentinvention, include amine-based catalysts, bismuth-based catalysts,nickel-base catalysts, zirconium-based catalysts, zinc-based catalysts,aluminum-based catalysts, lithium-based catalysts, iron(II) chloride;zinc chloride; lead octoate;tris(dialkylaminoalkyl)-s-hexahydrotriazines includingtris(N,N-dimethylaminopropyl)-s-hexahydrotriazine; tetraalkylammoniumhydroxides including tetramethylammonium hydroxide; alkali metalhydroxides including sodium hydroxide and potassium hydroxide; alkalimetal alkoxides including sodium methoxide and potassium isopropoxide;and alkali metal salts of long-chain fatty acids having from 10 to 20carbon atoms and/or lateral OH groups.

Further examples of other suitable catalysts, specifically trimerizationcatalysts, for purposes of the present invention, includeN,N,N-dimethylaminopropylhexahydrotriazine, potassium, potassiumacetate, N,N,N-trimethyl isopropyl amine/formate, and combinationsthereof. A specific example of a suitable trimerization catalyst iscommercially available from Air Products and Chemicals, Inc. under thetrade name POLYCAT®.

Yet further examples of other suitable catalysts, specifically tertiaryamine catalysts, for purposes of the present invention, include1-methylimmidazol, DABCO 33-LV dimethylaminoethanol,dimethylaminoethoxyethanol, triethylamine,N,N,N′,N′-tetramethylethylenediamine, N,N-dimethylaminopropylamine,N,N,N′,N′,N″-pentamethyldipropylenetriamine,tris(dimethylaminopropyl)amine, N,N-dimethylpiperazine,tetramethylimino-bis(propyl amine), dimethylbenzylamine, trimethylamine,triethanolamine, N,N-diethyl ethanolamine, N-methylpyrrolidone,N-methylmorpholine, N-ethylmorpholine, bis(2-dimethylamino-ethyl)ether,N,N-dim ethyl cyclohexylamine (DMCHA),N,N,N′,N′,N″-pentamethyldiethylenetriamine, 1,2-dimethylimidazole,3-(dimethylamino) propylimidazole, and combinations thereof. Specificexamples of suitable tertiary amine catalysts are commercially availablefrom Air Products and Chemicals, Inc. under the trade name POLYCAT®,e.g. POLYCAT® 41.

If employed, the catalyst component can be employed in various amounts.Typically, the catalyst component is used in an amount to ensureadequate open/working time. It is to be appreciated that the catalystcomponent may include any combination of the aforementioned catalysts.

The system may be supplied to consumers for use by various means, suchas in railcars, tankers, large sized drums and containers or smallersized drums, kits and packets. For example, one kit can contain theisocyanate component and another kit can contain the resin component.Providing the components of the system to consumers separately providesfor increased formulation flexibility of the elastomeric compositionsformed therefrom. For example, a consumer can select a specificisocyanate component and a specific resin component, and/or amountsthereof, to prepare an elastomeric composition.

The isocyanate and resin components typically have excellent storagestability or “free” stability. As such, the isocyanate and resincomponents can be separately stored (as the system) for extended periodsof time before combining them to form the elastomeric composition. It isto be appreciated that the system can comprise two or more differentisocyanate components and/or two or more different resin components,which can be employed to prepare the elastomeric composition. It is alsoto be appreciated that other components (e.g. the supplemental polyol,the additive component, etc.), if employed, can be supplied in theaforementioned isocyanate and/or resin components, or supplied asdistinct components.

The present invention further provides a composite material. Thecomposite material comprises aggregate and the elastomeric composition.The elastomeric composition is generally formed from the isocyanate andresin components, as described and exemplified above. As introducedabove, in certain embodiments, the isocyanate component comprises thepolymeric isocyanate, and optionally, the isocyanate-prepolymer. Inother embodiments, the isocyanate component comprises the polymericisocyanate and the isocyanate-prepolymer. The isocyanate-reactivecomponent comprises the hydrophobic polyol and the chain extender.

The amount of elastomeric composition present in the composite materialgenerally depends on the particle size of the aggregate. Typically, thelarger the aggregate particle size, the less elastomeric composition isrequired to form the composite material, and the smaller the aggregatesize, the more elastomeric composition is required to form the compositematerial. Smaller sized aggregate generally requires more elastomericcomposition because there is more surface area to coat relative tolarger sized aggregate. For example, with 0.25 inch aggregate, theelastomeric composition is typically present in the composite materialin an amount of from about 1.0 to about 10.0, more typically from about2.5 to about 5.0, and yet more typically about 4.2, parts by weight,each based on 100 parts by weight of the composite material.

As used herein, the term aggregate is to be interpreted as referring toaggregate or aggregates in general and not to a single aggregate, nor isit to be construed to require more than one aggregate. Additionally, theterm aggregate, as used herein, is intended to encompass a broadcategory of materials that serves as reinforcement to the compositematerial, such as rock, glass, rubber crumb, architectural stone, etc.The term rock, as used herein, is intended to encompass all forms ofrock, including, but not limited to, gravel, sand, etc. Additionally,the term rock as used herein is intended to encompass all species ofrock, such as granite, limestone, marble, etc.

In certain embodiments, the aggregate comprises rock. It is to beappreciated that any type of rock can be used. The rock is typicallyselected from the group of granite, limestone, marble, beach stone,river rock, and combinations thereof. In a specific embodiment, the rockis granite.

The rock is typically present in the aggregate in an amount of fromabout 1 to about 100, more typically from about 50 to about 100, yetmore typically from about 90 to about 100, and yet even more typicallyabout 100, parts by weight, each based on 100 parts by weight of theaggregate in the composite material. The remainder of the aggregate, ifany, can be another different aggregate, such as sand, gravel, etc.

The average diameter of the rock is typically from about 0.001 to about7.0, more typically from about 0.10 to about 5.0, yet more typicallyfrom about 0.25 to about 5.0, and yet even more typically from about 0.5to about 3.0, inches. In other embodiments, the rock may be larger orsmaller in size.

In certain embodiments, the aggregate comprises rubber crumb. It is tobe appreciated that any type of rubber crumb can be used. Although notrequired, the rubber crumb may be post-consumer and/or recycled rubber.The rubber crumb can be of various classifications, such as No. 1, 2, 3,4, and/or 5.

The rubber crumb is typically present in the aggregate in an amount offrom about 1 to about 100, more typically from about 50 to about 100,yet more typically from about 90 to about 100, and yet even moretypically about 100, parts by weight, each based on 100 parts by weightof the aggregate in the composite material. The remainder of theaggregate, if any, can be another different aggregate, such as sand,gravel, etc.

The average diameter of the rubber crumb is typically from about 0.10 toabout 3.0, more typically from about 0.10 to about 2.0, and yet moretypically from about 0.10 to about 0.25, inches. Suitable grades ofrubber crumb, for purposes of the present invention, are commerciallyavailable from Entech Inc. of White Pigeon, Mich.

In certain embodiments, the aggregate comprises glass. It is to beappreciated that any type of glass may be used for purposes of thepresent invention. The glass may be clear, tinted, and/or colored.Although not required, the glass may be post-consumer and/or recycledglass. Using such glass can reduce the overall cost of the compositematerial and reduce the environmental footprint.

The glass is typically present in the aggregate in an amount of fromabout 1 to about 100, and more typically from about 50 to about 100, yetmore typically from about 80 to about 100, and yet even more typicallyabout 100, parts by weight, each based on 100 parts by weight of theaggregate present in the composite material. The remainder of theaggregate, if any, can be another different aggregate, such as sand,gravel, etc. It is believed that increasing the amount of glass presentin the aggregate improves the flexural modulus and compressive strengthof the composite material.

The average diameter of the glass is typically from about 0.001 to about1.0, more typically from about 0.10 to about 0.50, and yet moretypically from about 0.125 to about 0.25, inches. It is believed thatreducing the average diameter of the glass reduces spalling of theaggregate from the composite material (i.e., loosened or loose pieces ofglass) and improves resistance to flexural stresses, such as stressesencountered from a tire being turned on the composite material. Whenemployed, the glass is typically crushed to meet the average diameterranges as described above. For safety, the glass is typically tumbled orvibrated over screens for rounding sharp edges of the glass. Suitablegrades of glass, for purposes of the present invention, are commerciallyavailable from Glass Plus Inc. of Tomahawk, Wis.

In certain embodiments, the glass includes a surface treatmentcomprising (or providing) at least one functional group reactive with anisocyanate group of the elastomeric composition. Examples of suitablefunctional groups, for purposes of the present invention, includehydroxyl, thiol, epoxy, and/or primary and secondary amine groups.Typically, the surface treatment comprises at least one amine and/oramino functional group. It is to be appreciated that the surfacetreatment can include a combination of different functional groups.

Surface treatment can be imparted to the glass by various methods, suchas by employing an aminosilane, more specifically an organofunctionalalkoxysilane, e.g. SILQUEST® A-1100, SILQUEST® A-1120, and/or SILQUEST®A-1170, which are commercially available from Momentive PerformanceMaterials of Albany, N.Y. For example, the glass can be washed andtreated with the aminosilane to impart the surface treatment to theglass. Said another way, the glass now includes one or more functionalgroups imparted by the aminosilane reacting with the glass. The glassmay be referred to as being “primed” or “silylated”. The functionalgroups, e.g. amine/amino groups, are reactive with isocyanate functionalgroups of the elastomeric composition. The isocyanate functional groupscan be free isocyanate functional groups after reaction to form theelastomeric composition, such as in instances of over indexing, orisocyanate functional groups imparted by one or more components of theelastomeric composition itself, e.g. the isocyanate-prepolymer, suchthat the functional groups of the glass become part of the reaction toform the elastomeric composition.

It is believed that surface treating the glass improves durability,reduces spalling of the aggregate, and increases strength of thecomposite material. This is especially true if a chemical bond formsbetween the elastomeric composition and the surface of the glass. Forexample, one or more —Si—O— bonds may be present between the surface ofthe glass and the elastomeric composition. It is also believed that thesurface treatment makes the composite material much more stable toenvironmental forces, such as heat and humidity, which could potentiallyreduce its strength during application. In certain embodiments, theglass used as the aggregate of the present invention comprises the glassaggregate described in co-pending application PCT/US10/58582,incorporated herein by reference in its entirety to the extent that thedisclosure does not conflict with the general scope of the presentinvention described herein. PCT/US10/58582 describes various methods forsurface treating glass aggregate, as well as benefits of surfacetreatment which is imparted to the composite material of the presentinvention.

It is to be appreciated that the aggregate may include a combination oftwo or more of the aforementioned aggregates. For example, the aggregateof the composite material can comprise glass and rock. In theseembodiments, the glass is typically present in the aggregate an amountof from about 1.0 to about 99, more typically from about 25 to about 99,and yet more typically from about 75 to about 99, parts by weight, eachbased on 100 parts by weight of the aggregate present in the compositematerial. Further, the rock is typically present in the aggregate in anamount of from about 99 to about 1.0, more typically from about 75 toabout 1.0, and yet more typically from about 25 to 1.0, parts by weight,each based on 100 parts by weight of the aggregate present in thecomposite material.

The aggregate can be supplied to consumers for use by various means,such as in railcars, tankers, large and small sized supersacks, largesized drums and containers or smaller sized drums, kits and packets. Asdescribed and exemplified above for description of the system, providingthe components of composite material to consumers separately providesfor increased formulation flexibility of the composite materials formedtherefrom. For example, a consumer can select a specific aggregate, aspecific isocyanate component, and a specific resin component, and/oramounts thereof, to prepare the composite material.

Typically, the aggregate is dry (but for possible ambient humidity, ifpresent), to prevent premature reaction with the isocyanate component ofthe system. In addition, it is believed that curing and bonding strengthof the elastomeric composition can be improved when the aggregate isdry. The aggregate can be kept dry by various methods, such as by usingwaterproof or water-resistant supersacks. However, in certainembodiments, the aggregate can at least be partially or completelysubmerged underwater, as described further below. It should also beappreciated that the aggregate may already be present in the locationdesired to include the composite material, e.g. a railroad bed or alonga coast line. As such, the aggregate may not need to be separatelyprovided.

Further examples of suitable components, for purposes of the presentinvention, are generally described in U.S. Patent Publication Nos.2009/0067924 and 2009/0067295, both to Kaul, the disclosures of which,as well as the disclosures of patents and publications referencedtherein, are incorporated herein by reference in their entirety to theextent that the disclosures do not conflict with the general scope ofthe present invention described herein.

In certain embodiments, the composite material has a crush strength (orcompressive strength) of from about 100 to about 2500, more typicallyfrom about 500 to about 1800, yet more typically from about 1300 toabout 1600, and yet even more typically about 1500, psi, according toASTM D 1621. In certain embodiments, the composite material typicallyhas a flexural strength of from about 50 to about 1000, more typicallyfrom about 200 to about 1000, yet more typically from about 700 to about1000, and yet even more typically about 700, psi, according to ASTM D790. In certain embodiments, the composite material typically has aflexural modulus of from about 20000 to about 150000, more typicallyfrom about 50000 to about 150000, yet more typically from about 100000to about 150000, and yet even more typically about 100000, psi,according to ASTM D 790.

In certain embodiments, the composite material has a porosity (or voidvolume) of from about 30 to about 50, more typically from about 34 toabout 45, yet more typically from about 35 to about 42, and yet evenmore typically from about 37 to about 38, %. Porosity of the compositematerial can be determined by various methods understood in the art,such as: Montes, F., Valavala, S., and Haselbach, L. “A New Test Methodfor Porosity Measurements of Portland Cement Pervious Concrete,” J. ASTMInt. 2(1), 2005 and Crouch, L. K., Cates, M., Dotson, V. James, Jr.,Honeycutt, Keith B., and Badoe, D. A. “Measuring the Effective Air VoidContent of Portland Cement Pervious Pavements,” ASTM Journal of Cement,Concrete, and Aggregates, 25(1), 2003.

Increasing the porosity of the composite material is useful for reducingrun-off, such as rain run-off. In certain embodiments, the voidfractions can also reduce hydrocarbons. For example, hydrocarbons, suchas motor oil dripping from an automobile, can flow down through theporous composite material and adsorb onto the aggregate particles, e.g.glass, where the hydrocarbons can be digested by bacteria over time,thus preventing the hydrocarbons from contaminating the soil and/orgroundwater.

It is believed that the porosity of the composite material allows thecomposite material to accept very large volumes of water in a shortperiod of time. In certain embodiments, testing of a pavement structureformed from the composite material indicated that the pavement structurecan accept about 1600 inches of water per hour. Also, it is believedthat the porosity makes the maintenance of pavement structures formedfrom the composite material easier because sediment deposited in thepores can be removed with little effort. Air flow through the compositematerial also allows it to release heat through convection much quickerthan conventional pavements so the pavement structure cools down in amuch shorter period of time after a heat source is removed relative toconventional pavements.

In certain embodiments, the composite material has a permeability offrom about 500 to about 4000, more typically from about 1000 to about3000, yet more typically from about 1500 to about 2000, and yet evenmore typically about 1650, inches/hour. Permeability of the compositematerial can be determined by various methods understood in the art,such as: Montes, F., Haselbach, L. “Measuring Hydraulic Conductivity inPervious Concrete,” Env. Eng. Sci. 23(6), 2006 and Schaefer, V., Wang,K., Suleimman, M. and Kevern, J. “Mix Design Development for PerviousConcrete in Cold Weather Climates,” Final Report, Civil Engineering,Iowa State University, 2006. Increasing the permeability of thecomposite material is useful for reducing runoff. In other embodiments,such as those described further below, the composite material isnonporous.

In certain embodiments, the elastomeric composition, upon approaching orreaching a final cure state, typically has a tensile strength of fromabout 1000 to about 3000, more typically from about 1500 to about 3000,yet more typically from about 2000 to about 3000, and yet even moretypically about 2300, psi, according to ASTM D 412 and/or ASTM D 638. Incertain embodiments, the elastomeric composition, upon approaching orreaching a final cure state, typically has an elongation of from about20 to about 150, more typically from about 60 to about 150, yet moretypically from about 90 to about 150, and yet even more typically about100, %, according to ASTM D 412 and/or ASTM D 638.

In certain embodiments, the elastomeric composition, upon approaching orreaching a final cure state, typically has a (Grave's) tear strength offrom about 50 to about 400, more typically from about 200 to about 400,yet more typically from about 325 to about 400, and yet even moretypically about 365, ppi, according to ASTM D 624. In certainembodiments, the elastomeric composition, upon approaching or reaching afinal cure state, typically has a durometer Shore D hardness of fromabout 20 to about 60, more typically from about 40 to about 60, yet moretypically from about 50 to about 60, and yet even more typically about54, according to ASTM D 2240. In certain embodiments, the elastomericcomposition, upon approaching or reaching a final cure state, typicallyhas a peel strength of from about 30 to about 80, more typically fromabout 50 to about 80, yet more typically from about 65 to about 80, andyet even more typically about 75, ppi, according to ASTM D 6862.

As described above, in certain embodiments, the elastomeric compositioncomprises the reaction product of the isocyanate-prepolymer, thepolymeric isocyanate, the hydrophobic polyol, and the chain extender. Inother embodiments, the elastomeric composition comprises the reactionproduct of an intermediate-prepolymer, the hydrophobic polyol, and thechain extender.

In the embodiments employing the intermediate-prepolymer, theintermediate-prepolymer is equivalent to the isocyanate component. Saidanother way, if employed, the intermediate-prepolymer takes place of theisocyanate component, and therefore, serves as the isocyanate componentin such embodiments and descriptions thereof.

The intermediate-prepolymer typically comprises the reaction product ofthe isocyanate-prepolymer, the polymeric isocyanate, and the hydrophobicpolyol. Optionally, the intermediate-prepolymer may comprise the furtherreaction product of the chain extender. Alternatively, theintermediate-prepolymer comprises the reaction product of theisocyanate-prepolymer, the polymeric isocyanate, and the chain extender.Optionally, the intermediate-prepolymer may comprise the furtherreaction product of the hydrophobic polyol.

Typically, the entire amount of the isocyanate-prepolymer and thepolymeric isocyanate used to form the elastomeric composition isemployed to form the intermediate-prepolymer. In contrast, only aportion of the hydrophobic polyol and/or the chain extender is used toform the intermediate-prepolymer, while the remainder of the hydrophobicpolyol and/or the chain extender is left for use as the resincomposition.

If employed, the intermediate-prepolymer is useful for achieving adesired NCO content of the isocyanate component, altering curingproperties of the elastomeric composition, and altering viscosity of theelastomeric composition. The intermediate-prepolymer is especiallyuseful for use in moist or wet conditions, as alluded to above and asdescribed further below. Other advantages can also be appreciated withreference to the Example section below.

The present invention further provides a method of forming theelastomeric composition. The method comprises the steps of providing theisocyanate-prepolymer, the polymeric isocyanate, the hydrophobic polyol,and the chain extender. In certain embodiments, the method furthercomprises the step of reacting the isocyanate prepolymer and thepolymeric isocyanate with the hydrophobic polyol to form theintermediate-prepolymer. In this embodiment, the method furthercomprises the step of reacting the intermediate-prepolymer with theresin component form the elastomeric composition. Typically, theintermediate-prepolymer is formed separate from the resin component.Alternatively, as like described above, the intermediate-prepolymercomprises the reaction product of the isocyanate-prepolymer, thepolymeric isocyanate, and the chain extender.

In one embodiment, the step of forming the elastomeric composition isfurther defined as the separate steps of first reacting the isocyanateprepolymer and the polymeric isocyanate with an amount of thehydrophobic polyol, and optionally, an amount of the chain extender, toform the intermediate-prepolymer. Next, the intermediate-prepolymer isreacted with the remainder of at least one of the chain extender and thehydrophobic polyol (i.e., the resin component) to form the elastomericcomposition.

The present invention further provides a method of forming the compositematerial. The method comprises the steps of providing aggregate andforming the elastomeric composition. The method further comprises thestep of applying the elastomeric composition to the aggregate to formthe composite material.

The elastomeric composition can be formed by various methods, such asthose described above. In one embodiment, the method comprises the stepsof providing the isocyanate-prepolymer, providing the polymericisocyanate, providing the hydrophobic polyol, and providing the chainextender. The method comprises the further step of reacting theisocyanate prepolymer and the polymeric isocyanate with the hydrophobicpolyol to form an intermediate-prepolymer. Typically, the isocyanateprepolymer and the polymeric isocyanate are mixed prior to the step ofreacting the isocyanate prepolymer and the polymeric isocyanate with thehydrophobic polyol. The method comprises the further step of reactingthe intermediate-prepolymer with the resin composition to form theelastomeric composition. Typically, the steps of reacting occurindependent from each other.

When formed from the isocyanate and resin components, the isocyanateindex of the elastomeric composition is typically from about 70 to about200, more typically from about 90 to about 175, yet more typically fromabout 100 to about 175, yet even more typically from about 105 to about168, and yet even more typically about 121.

The elastomeric composition may be referred to in the art as a 2Kelastomeric polyurethane composition. The isocyanate and resincomponents are mixed to form the reaction product of the elastomericcomposition. The term reaction product as used herein is intended toencompass all stages of interaction and/or reaction between theisocyanate and resin components, including reaction products of theisocyanate and resin components, even when the reaction product contactsthe aggregate to form the composite material. Generally, the reactionproduct begins to form when the isocyanate and resin components comeinto contact with each other.

Typically, the step of applying is further defined as coating theaggregate with the elastomeric composition. A suitable method of coatingincludes tumble-coating the aggregate with the elastomeric compositionin an apparatus. Suitable apparatuses include, but are not limited to,those described further below. Typically, the steps of forming andapplying are contemporaneous.

In certain embodiments, the composite material is at least partiallysubmerged underwater after the step of applying the elastomericcomposition to the aggregate. As such, the elastomeric composition curesto a final cure state while partially or completely submergedunderwater. Typically, a surface of the elastomeric composition, i.e.,an interface between the surface of the forming elastomeric compositionand the water, is substantially free of bubble formation during curingof the elastomeric composition while the composite material is submergedunderwater. The aforementioned lack of bubble formation is especiallytrue when the intermediate-prepolymer is employed, as alluded to above.These embodiments may be encountered along coast lines, as introducedabove.

Typically, the surface of the elastomeric composition is substantiallyfree of bubble formation during the step of applying the elastomericcomposition. Specifically, the hydrophobic nature of the elastomericcomposition leads to little to no bubbling at the surface of theelastomeric composition during formation, even in the presence of water,such as when the composite material is forming (i.e., curing)underwater. Said another way, little to no foaming occurs duringformation of the composite material. For example, if the isocyanate andresin components are mixed, degassed, and dumped into water while stillliquid and allowed to cure into a hard elastomer, the surface of theelastomer at the interface between the elastomer and the water generallyshows no sign of bubble formation, cloudiness, wrinkling, and/or anothertype of marring.

Generally, when the isocyanate and resin components are brought intocontact with each other, such as by mixing the isocyanate and resincomponents together, the isocyanate and resin components begin to reactto form the reaction product. The reaction product of the elastomericcomposition, during formation, adheres the aggregate together to formthe composite material. It is to be appreciated that the reactionproduct can begin to form over a period of time prior to introducing theaggregate. This is especially true if the composite article is to beformed partially or completely underwater. For example, the reactionproduct may be allowed to react for about 1 to about 25 minutes prior tointroducing the aggregate. Typically, the aggregate is introduced beforethe reaction product reaches a final cure state. It is also to beappreciated that the reaction between the isocyanate and resincomponents may be delayed for some period of time after the isocyanateand resin components are brought into contact with each other.

The reaction between the isocyanate and resin components is commonlyreferred to in the art as a crosslink or crosslinking reaction, whichgenerally results in build-up of molecular chains, i.e., molecularweight, in the reaction product to produce a crosslinked structure.Reaction of the isocyanate and resin components can occur at varioustemperatures, such as room or ambient temperature, although heating maybe applied to one or more of the components to trigger and/or acceleratereaction between the isocyanate and resin components. In certainembodiments, although dependent in part on the specific componentsemployed, application of heat accelerates reaction between theisocyanate and resin components. Typically, at least one of the steps ofreacting occurs in at least one reaction vessel, such as when theintermediate-prepolymer is formed.

The composite material can be used for various applications and invarious locations. For example, the composite material can be molded,screed, compacted or flattened to form pavement. Examples ofapplications employing the composite material include, but are notlimited to, forming revetments, rail-road track beds, pavement,sidewalks, patios, tracks, playground surfaces, trails, landscapefeatures, boat launch areas, etc. Such applications of the compositematerial can be used to prevent erosion and/or to reduce soundtransmission. The aforementioned applications can be formed by methodsunderstood by those skilled in respective art, such as the civilengineering and road construction arts. For example, a conventionalpaving process can be used but for the replacement of concrete with thecomposite material of the present invention.

As a further example, certain embodiments of pavement can be formed andfinished similar to low slump concrete. The composite material can bemixed in a batch process, on a small scale, using a concrete or mortarmixer. The elastomeric composition is mixed and added to the aggregatein the mixer, blended for a few minutes and then placed into forms. Avibratory screed can be used to provide a slight compaction/settling ofthe composite material in the forms. A smooth finish can be achieved byworking the surface with a bull float (Fresno blade) or a power trowel,and the edges around the forms can be finished with an edge trowel.

Depending on weather conditions, the composite material can be tack freewithin about 4 to 6 hours, can be walked on in about 24 hours, andtypically has achieved about 95% of its final hardness within 72 hours.If the surface is to be driven on, it can typically withstand the forceof vehicle traffic after about 4 days. Optionally, an aliphaticpolyurethane surface coating can be sprayed or rolled on after thecomposite material is tack free to ensure a wearing surface that is verystable to torsional forces, such as from tires turning upon it. Also,sand or other small aggregate or fines can be broadcast over the curingtop coat to provide an anti-skid surface on slopes or areas with highfoot traffic.

Typically, the composite material, once cured, is self-supporting. Saidanother way, a support structure is not required to support, or to beembedded within, the composite material. An example of a conventionalsupport structure used for paving applications is GEOBLOCK®,commercially available from PRESTOGEO SYSTEMS® of Appleton, Wis. Onedisadvantage of using such a support structure is that the supportstructure has a coefficient of thermal expansion significantly greaterthan a coefficient of thermal expansion of the aggregate of thecomposite material, e.g. glass. Specifically, the coefficient of thermalexpansion of the aggregate is typically less than the coefficient ofthermal expansion of the support structure. The difference between thecoefficient of thermal expansion between the aggregate and the supportstructure can result in failure of the composite material.

As such, in certain embodiments of the present invention, the compositematerial of the present invention, once cured, is completely free of asupplemental support structure, e.g. GEOBLOCK®. For example, thecomposite material can be used for paving applications without relyingon the support structure. Surprisingly, the elastomeric composition ofthe present invention allows for the exclusion of such supportstructures, which can negatively impact cured composite articlesincluding them, such as by warping or buckling pavement because ofthermal expansion and contraction differences between the compositematerial and the embedded or underlying support structure.

The composite material either before or after final cure state, can beformed into various shapes of varying dimensions. For example, thecomposite material can essentially be planar (e.g. when the compositematerial is employed as pavement) having a thickness of from about 0.5to about 6.0, more typically from about 1.0 to about 4.0, and yet moretypically from about 2.0 to about 3.0, inches. It is to be appreciatedthat thickness of the composite material, depending on its application,may be uniform or may vary.

Once the elastomeric composition of the composite material begins tocure, the composite material only remains pliable or workable for alimited time until the composite material reaches a cure state such thatthe composite material is no longer pliable or workable. Typically, thecomposite material has a working time of from about 1 to about 40, moretypically from about 1 to about 30, and yet more typically from about 1to about 20, minutes. In one embodiment, the composite material has aworking time of from about 30 to 45 minutes. Once the elastomericcomposition fully cures, the composite material is fully formed. Thecomposite material, even when fully cured, may be further processed,such as by cutting or sanding the composite material for variousapplications. Final cure time of the composite material can be affectedby many variables. Typically, the composite material reaches a finalcure state after about 30 days at an average temperature of about 72° F.and an average relative humidity of about 50%.

In the methods above, the step of coating the aggregate with theelastomeric composition can be accomplished through many differentmethods and can be a batch, semi-batch, or a continuous process. In oneembodiment, the aggregate and the elastomeric composition are mixed fora period of time. It should be appreciated that the elastomericcomposition may be formed prior to or during introduction to theaggregate. Alternatively, the aggregate, the isocyanate component, andthe resin component, may be introduced simultaneously and mixed. Theorder of addition of the components to form the composite material canbe of any order. The period of time referred to above is the period oftime for which the elastomeric composition is mixed with the aggregate.The period of time is sufficient to coat the aggregate with theelastomeric composition and is typically from about 10 seconds to about10 minutes, and more typically from about 10 seconds to about 5 minutes.The aggregate coated with the elastomeric composition is typicallyremoved from the mixer or any other apparatus prior to full curing ofthe elastomeric composition to form the composite material.

The elastomeric composition and the aggregate may be mixed by any methodknown in the art, including rotating drums, tumblers, single-shaft batchmixers, twin-shaft batch mixers, spiral-bladed drums, etc. In anotherembodiment of the present invention, the step of coating the aggregatewith the elastomeric composition is accomplished by spraying. In thisembodiment, the elastomeric composition can be at least partially formedbefore or during the step of spraying. Spraying can be accomplished byany method known in the art, such as by impingement mixing of thecomponents in the elastomeric composition, mechanical mixing andspraying, etc. A specific example of a suitable apparatus for formingthe composite material is disclosed in PCT/EP2010/058989, which isincorporated herewith by reference in its entirety. It should beappreciated that the aggregate may be stationary or, alternatively, theaggregate may be disposed in a tumbler or other moveable drum toincrease the surface area of the aggregate exposed to the sprayedelastomeric composition as the aggregate is in motion in the tumbler orthe other moveable drum. The aggregate could also be sprayed while therock is disposed along an area, e.g. a coastal area, which the compositematerial is to be formed on. As described above, when the aggregate issprayed while the aggregate is in the tumbler, the aggregate coated withthe elastomeric composition is typically removed from the tumbler priorto fully curing the elastomeric binding composition to form thecomposite material.

When the elastomeric composition is sprayed, it should be appreciatedthat the isocyanate component and the resin component may be mixedbefore or after exiting a nozzle of the sprayer. In one embodiment, theresin and isocyanate components are separate streams when exiting thenozzle of the sprayer and mix prior to coating the aggregate. In otherembodiments, the resin and isocyanate components are premixed prior toleaving the nozzle of the sprayer. For example, in one embodiment, theintermediate-prepolymer is formed prior to forming the elastomericcomposition.

After the aggregate is coated with the elastomeric composition, andafter optional mixing of the same, the elastomeric composition cures toform the composite material. In embodiments where the aggregate, e.g.rock, and the elastomeric composition are mixed in the mixer, theelastomeric composition is typically cured outside of the mixer. Forexample, the composite material can be placed along a coastal area thatis to be reinforced prior to full curing of the elastomeric composition.

It should be appreciated that at least one layer, such as a compensatinglayer, may be placed on the coastal area prior to placing the aggregatecoated with the elastomeric composition thereon to further increase thedurability and adhesion of the composite material. In one embodiment,the compensating layer is placed on the coastal area and the aggregatecoated with the elastomeric composition is placed thereon prior to fullycuring the elastomeric composition. Curing of the elastomericcomposition is typically passive, i.e., there is no need for anaffirmative step, such as heating, etc., to cure the bonding compositionand curing naturally occurs.

Typically, the need for the composite material exists where water isposing a current threat of erosion of a coastal area, and thereforeremoval of water can be time consuming, difficult, and burdensome. Theelastomeric composition, especially when the intermediate-prepolymer isemployed, can be cured in the presence of water while maintainingexcellent cohesive strength between the elastomeric composition andaggregate, e.g. rock. The ability to cure in the presence of water isattributable to the components of the system, such as the hydrophobicpolyol. The presence of water can be from various sources, such as rain,high tide, waves from a body of water adjacent the coastal area, etc. Inaddition, as described above, it should be appreciated that theelastomeric composition can be cured while underwater, i.e., whilepartially or completely submerged, while maintaining excellent cohesionbetween the elastomeric composition and aggregate, excellent durability,and excellent compressibility of the composite material formedtherefrom. The ability to cure underwater greatly enhances theversatility of the elastomeric composition and composite material formedtherefrom.

The composite material can also be at least partially cured in a mold,which may be closed-type or open-type mold. The mold can define a cavitythat substantially encapsulates the aggregate coated with theelastomeric composition or, alternatively, can define an open cavitythat does not substantially encapsulate the aggregate coated with theelastomeric composition. Additionally, the mold can be a reactioninjection mold (RIM) wherein the isocyanate and resin components areseparately injected into the mold having the aggregate disposed therein.Molds can be useful for forming various shapes of the compositematerial, such as bricks.

To reiterate, depending in part on the environment in which the systemis employed, the hydrophobic polyol is useful in preventing and/orminimizing a competing reaction between the isocyanate-prepolymer, thepolymeric isocyanate, and water molecules. Additionally, the hydrophobicpolyol reacts with the isocyanate-prepolymer and/or the polymericisocyanate to form the elastomeric composition. Water and NCO functionalgroup containing components, i.e., the isocyanate-prepolymer and thepolymeric isocyanate, readily react in the presence of each other. Whena conventional composition is exposed to water prior to complete curing,the competing reaction between the water and the isocyanate componentscan have undesirable effects on the resulting conventional compositematerial, such as reduced durability, reduced cohesive strength, reducedtensile strength, etc. However, in the present invention, the resincomponent has a strong aversion for water, thereby reducing theinteraction and the competing reaction between the isocyanate componentand the water. When the composite material of the present invention isused for revetments, the elastomeric composition is frequently exposedto water prior to complete curing, as described above.

The composite pavement structure of the present invention will now bedescribed. The composite pavement structure comprises a base courselayer and a wearing course layer. The wearing course layer is typicallydisposed above the base course layer. The layers may be in contact withone another, or one or more intervening layers may separate the layersas described further below.

The wearing course layer comprises aggregate and an elastomericcomposition. The aggregate of the wearing course layer comprises fromabout 30 to 100 wt. % glass and from 0 to about 70 wt. % rock, eachbased on 100 parts by weight of the aggregate of the wearing courselayer. In certain embodiments, the aggregate comprises 100 wt. % glass.Rock can be added to provide aesthetic or functional changes in thewearing course layer. The aggregate of the wearing course layer is asdescribed and exemplified above with description of the compositematerial. A specific example of aggregate is surface treated glasshaving an average diameter of about 0.25 inches or less. As describedabove, the glass can include the surface treatment comprising at leastone of a silane group, a silanol group, or combinations thereof.Specific examples of suitable surface treated glass are described inPCT/US10/58582, as first introduced above. Surface treatment is usefulfor increasing bonding of the elastomeric composition to the aggregate.

The elastomeric composition is as described and exemplified above withdescription of the composite material. The elastomeric composition canbe present in the wearing course layer in various amounts, typically inan amount of from about 1 to about 10 parts by weight based on 100 partsby weight of the wearing course layer. It is to be appreciated thatadditional amounts of the elastomeric composition may also be employed,such as to reduce porosity of the wearing course layer by filling voidspaces thereof. In certain embodiments, the elastomeric compositionincludes the colorant component.

The aggregate of the base course can be the same as or different thanthe aggregate of the wearing course layer, such as being different intype, size, particle size distribution, etc. The aggregate of the basecourse layer is as described and exemplified above with description ofthe composite material. Specific examples of aggregate include crushedstone, e.g. limestone, having an average diameter of from about 0.375 toabout 0.75 inches or glass having an average diameter of from about0.375 to about 0.5 inches. The aggregate of the base course layer isunbound, whereas the aggregate of the wearing course layer is bound bythe elastomeric composition.

Typically, the wearing course layer is porous; however, in certainembodiments, the wearing course layer is nonporous. Porosity of thewearing course layer can be controlled by the level of compaction of thewearing course layer, and/or by the methods as described and exemplifiedabove, e.g. increased elastomeric composition, use of fines, etc.

In certain embodiments, both of the wearing and base course layers areporous. Porosity of the base course layer can be controlled by the levelof compaction of the base course layer, e.g. compacted to about 90%modified proctor, by size distribution of the aggregate, etc.

The composite pavement structure can further comprise a choker courselayer, which is sandwiched between the wearing and base course layers,The choker course layer comprise aggregate and is different than thewearing and base course layers. The aggregate of the choker course isdifferent than the aggregate of the wearing and base course layers, suchas being different in type, size, particle size distribution, etc. Theaggregate of the choker course layer is as described and exemplifiedabove with description of the composite material. Specific examples ofaggregate include crushed aggregate having an average diameter of fromabout 0.25 to about 0.375 inches. The aggregate of the choker courselayer is unbound. The choker course layer can be useful for preventingmigration of sedimentation through the pavement structure or layersthereof.

The composite pavement structure can further comprise a geosyntheticlayer, which is disposed under the wearing course layer. If employed,the geosynthetic layer can also be disposed under the choker courselayer (if also employed), under the base course layer, or in acombination of locations. It is to be appreciated that the geosyntheticlayer can even partially envelope one of the other layers, such as outeredges of the base course layer. Examples of suitable geosynthetics,include geotextiles, geogrids, geonets, geomembranes, geosynthetic clayliners, geofoam, drainage/infiltration cells, geocomposites, etc. Incertain embodiments employing the geosynthetic layer, the geosyntheticlayer is a geotextile, such as a non-woven geotextile. If employed, thegeotextile should have a sufficient infiltration rate, such as about 90gal/min per ft². The geosynthetic can be useful for preventing migrationof sedimentation through the pavement structure or layers thereof.

The composite pavement structure can further include a surface overcoatdisposed on a surface of the wearing course layer opposite the basecourse layer. The surface overcoat can be formed to various thicknesses,such as 5 mils or greater, and may comprise the elastomeric composition.If the surface overcoat is not formed from the elastomeric composition,it should be formed from a UV stable composition, such as from a UVstable polyurethane elastomer composition. UV stability can be impartedvia use of one or more additives understood in the art, and/or from useof an aliphatic isocyanate. The surface overcoat is useful to preventspalling of the aggregate from the wearing course layer. The surfaceovercoat can also be used for reducing porosity of the pavementstructure. Sand or other fines may be sprinkled on the wearing courselayer prior to the elastomeric composition reaching a final cure stateto provide skid resistance. The surface overcoat may be tinted with acolorant to provide an aesthetic appearance or be left naturallycolored. The surface overcoat can be applied to the wearing course layerby spraying and/or by rollers.

The composite pavement structure may be formed by various methodsunderstood in the art, such as by a method employed to form conventionalpavements. The composite pavement structure can be formed on- oroff-site. Typically, the composite pavement structure is formed at asite where a roadway, pathway, parking lot, thoroughfare, causeway,etc., is desired.

Methods of forming the composite pavement structure will now bedescribed, more specifically, methods of paving an area with thecomposite pavement structure will be described. The area can be aboveground, such as an area defined by forms or a mold, or can be ground ora similar structure itself. The present invention is not limited to anyparticular area. The area generally includes a cavity. The cavity may beformed by digging out a portion of ground, or by preparing forms aboveground where the forms define the cavity. It is to be appreciated thatforms can also be used below ground.

The method comprises the step of disposing aggregate into the cavity toform the base course layer. This can be done merely by dumping and,optionally, leveling an amount of aggregate in the cavity. As describedabove, the base course layer may be compacted to reduce porosity of thebase course layer.

The method further comprises the step of coating the aggregate of thewearing course layer with the elastomeric composition to form acomposite material. The composite material is generally the same as thecomposite material described and exemplified above. Coating of theaggregate can be achieved in various ways, such as by spraying ortumbling the aggregate with the elastomeric composition. For example,the composite material can be formed in an auger/mixer, or an apparatusas described and exemplified above. Typically, tumble-coating willprovide a stronger composite material, once cured. The aggregate can beheld in water proof super sacks for delivery to the site. The componentsof the elastomeric binder composition can be held in containersincluding desiccant means until employed, such as desiccant cappedcontainers. Minimizing water contamination is useful for preventingpremature reaction of the elastomeric composition during formation ofthe wearing course layer.

The method further comprises disposing the composite material into thecavity to form the wearing course layer, such as physically dumping andoptionally, leveling, the composite material in the cavity. As describedabove, the wearing course layer may be compacted to reduce porosity ofthe wearing course layer.

The method can include one or more optional steps, depending on theembodiment of the composite pavement structure. These steps generallyinclude: disposing a geosynthetic into the cavity to form thegeosynthetic layer; disposing aggregate into the cavity to form thechoker course layer; positioning forms about a perimeter of the area;screeding the composite material; compacting the composite material toreduce porosity of the wearing course layer; finishing a surface of thewearing course layer to orient the aggregate of the surface into aplanar relationship with each other and impart the surface with a flatprofile in cross-section to resist spalling of the wearing course layer;and applying an overcoat to the surface of the wearing course layerafter the step of finishing to form the surface overcoat.

If employed, screeding can be accomplished with a power screed, rollerscreed, hand screed, screeds having magnesium strikes or vibrastrikes,etc. Finishing the surface of the wearing course layer can be achievedby manipulating a finishing tool along the surface to finish the surfaceof the wearing course layer. Suitable tools include a power trowel, afresco blade, etc. Other equipment for forming and finishing thecomposite pavement structure are described and exemplified above withdescription of the composite material. For example, a telebelt can beused to dispose the composite material in front of a screed whiledisposing and screeding the composite material to form the wearingcourse layer.

The method can also include grading (or segregating) aggregate for usein the wearing course layer. Grading can be achieved by conventionalgraders. In certain embodiments, the aggregate, e.g. glass, of thewearing course layer has no more than 5% fines passing a #200 mesh. Incertain embodiments, the same is true for the aggregate of the basecourse and choker course layers. Keeping fines to a minimum helps tomaximize porosity of the composite pavement structure. Segregating theaggregate into different average diameter ranges for each of therespective layers also helps to maintain the porous nature of thepavement structure to maximum water handling. An example of an aggregategradation for an embodiment of the wearing course layer is shown belowin TABLE A below. It is to be appreciated that the present invention isnot limited to the particular numbers shown and that other ranges anddistributions may also be used.

TABLE A Sieve Size Sieve Opening % of Aggregate (in) (in) (¼ Inch orless) ⅜ 0.375 0 4 0.187 9 5 0.157 13 8 0.0937 46 10 0.0787 11 12 0.066112 20 0.0331 11 Pan 0 2

Referring now to the Figures, FIG. 1 is a partial cross-sectional viewof a pavement structure 20 illustrating water migration 22 through thepavement structure 20. The pavement structure 20 includes the wearingcourse layer 24 and the base course layer 26. The wearing course layer24 has a thickness T₁ and the base course layer 26 has a thickness T₂.

The wearing course layer 24 is typically porous; however, there areembodiments where the wearing course layer 24 is non-porous. ThicknessT₁ of the wearing course layer 24 can vary depending on end applicationsuch as for walking or driving pavements, i.e., driving pavements wouldbe thicker because of increased load requirements. The wearing courselayer 24 typically has an average thickness T₁ of from about 1 to about5, more typically from about 2.5 to about 3.5, inches. The same is truefor the base course layer 26; however, it is typically thicker than thewearing course layer 24. The base course layer 26 typically has anaverage thickness T₂ of at least about 2, more typically from about 2 toabout 12, alternatively at least 4, yet more typically from about 4 toabout 8, inches. It is to be appreciated that the thicknesses T of eachof the layers 24, 26 are not drawn to scale and may be of larger orsmaller in size, and such thicknesses T can be uniform or may vary. Thepavement structure 20 may also include additional storage base orunderground storage (not shown) below the base course layer 26.

In order to place such the pavement structure 20, native soil 28 (or“ground”) is typically excavated to a depth appropriate for the regionalweather conditions and how the native soil 28 drains. In some Northernclimates this could be as much as 24 inches, if not more. It is to beappreciated that excavation may not be required, e.g. when the pavementstructure 20 is built on top of native soil 28.

FIG. 2 is a partial cross-sectional view of a pavement structure 20including a choker course layer 30. The choker course layer 30 has athickness T₃. Thickness T₃ of the choker course layer 30 can varydepending on end application such as for walking or driving pavements,i.e., driving pavements would be thicker because of increased loadrequirements. The choker course layer 30 typically has an averagethickness T₃ of from about 0.5 to about 2.5, more typically from about1.0 to about 2.05, yet more typically about 1.5, inches.

FIG. 3 is a partial cross-sectional view of a pavement structure 20including a geosynthetic layer 32. Thickness of the geosynthetic layer32 can vary depending on end application such as for walking or drivingpavements. While not shown, the geosynthetic layer 32 may extend intoand/or around another one of the layers, such as around the base courselayer 26. It is to be appreciated that certain embodiments of thepavement structure 20 may include the geosynthetic layer 32 and excludethe choker course layer 30.

FIG. 4 is an enlarged view depicting a porous embodiment of the wearingcourse layer 24, e.g. the wearing course layer 24 of FIG. 1. The wearingcourse layer 24 includes the elastomeric composition 34 in a cured stateand the aggregate 36. Typically, the cured elastomeric composition 34 issubstantially to completely free of bubbles and/or voids itself. Thewearing course layer 24 defines a plurality of void spaces 38. It is tobe appreciated that the aggregate 36 can either be completely orpartially encapsulated by the elastomeric composition 34. Typically,when the wearing course layer 24 is in a porous configuration, there arelittle to no fines within the wearing course layer 24 or void spaces 38thereof.

FIG. 5 is an enlarged view depicting a nonporous embodiment of thewearing course layer 24. As depicted, the void spaces 38 are smaller innumber and in size relative to the wearing course layer 24 depicted inFIG. 4. Such a transition of the wearing course layer 24 from a porousto nonporous state may occur from an increased amount of the elastomericcomposition 34 relative to the amount of aggregate 36, from increasedcompacting during installation, and/or from a different sizedistribution of the aggregate 36 where smaller aggregate 36 or evenfines (not shown) fills in many, if not all, of the void spaces 38. Inother embodiments (not shown), the wearing course layer 24 may have novoid spaces 38 whatsoever.

The following examples, illustrating the system, elastomericcompositions and composite materials of the present invention, areintended to illustrate and not to limit the invention.

Examples

Examples of the resin and isocyanate components of the system areprepared. Examples of the elastomeric composition are also prepared. Theresin and isocyanate components are formed by mixing their respectivecomponents in a vessel. The vessel is a container capable ofwithstanding agitation and having resistance to chemical reactivity. Thecomponents of the resin and isocyanate components were mixed using amixer for 1 to 3 minutes at 1000 to 3500 rpm. The resin and isocyanatecomponents were mixed in a similar manner to form the elastomericcompositions.

The amount and type of each component used to form the Resin andIsocyanate Components are indicated in TABLES I and II below with allvalues in parts by weight (pbw) based on 100 parts by weight of therespective Resin or Isocyanate Component unless otherwise indicated. Thesymbol ‘-’ indicates that the component is absent from the respectiveResin or Isocyanate Component.

TABLE I Resin Component Example 1 Example 2 Example 3 Hydrophobic Polyol1 73.00 — — Hydrophobic Polyol 2 20.00 — — Hydrophobic Polyol 3 — 69.50— Hydrophobic Polyol 4 — 15.23 — Hydrophobic Polyol 5 — 3.81 —Hydrophobic Polyol 6 — — 50.00 Supplemental Polyol — — 49.45 ChainExtender — — — Molecular Sieve 1 6.95 6.62 — Molecular Sieve 2 — — 0.50Aminosilane — — — Antifoaming Agent 1 0.05 — — Antifoaming Agent 2 —0.05 0.05 Fumed Silica — 4.79 — Resin Total 100.00 100.00 100.00Isocyanate Component Example 1 Example 2 Example 3 Isocyanate-prepolymer— — — Polymeric isocyanate 100.00 100.00 100.00 Isocyanate Total 100.00100.00 100.00 Elastomeric Composition Example 1 Example 2 Example 3Resin/Isocyanate 2.000 2.000 1.222 Weight Ratio Isocyanate Index 118 138124

TABLE II Resin Component Example 4 Example 5 Example 6 HydrophobicPolyol 1 — — — Hydrophobic Polyol 2 — — — Hydrophobic Polyol 3 — — —Hydrophobic Polyol 4 16.40 — — Hydrophobic Polyol 5 4.10 — — HydrophobicPolyol 6 78.45 91.95 92.45 Supplemental Polyol — — — Chain Extender — —— Molecular Sieve 1 — — 0.50 Molecular Sieve 2 0.50 0.50 — Aminosilane0.50 0.50 — Antifoaming Agent 1 — — — Antifoaming Agent 2 0.05 0.05 0.05Fumed Silica — — — Resin Total 100.00 100.00 100.00 Isocyanate ComponentExample 4 Example 5 Example 6 Isocyanate-prepolymer — 60.00 60.00Polymeric isocyanate 100.00 40.00 40.00 Isocyanate Total 100.00 100.00100.00 Elastomeric Composition Example 4 Example 5 Example 6Resin/Isocyanate 1.916 1.400 1.404 Weight Ratio Isocyanate Index 136 121121

Hydrophobic Polyol 1 is a branched polyether/polyester polyol having ahydroxyl value of from 160-185 mg KOH/g and a functionality of about3.5, commercially available from Cognis Corporation.

Hydrophobic Polyol 2 is a slightly branched polyether/polyester polyolhaving a hydroxyl value of from 210-245 mg KOH/g, and a functionality ofabout 2.1, commercially available from Cognis Corporation.

Hydrophobic Polyol 3 is a branched polyether/polyester polyol having ahydroxyl value of from 160-185 mg KOH/g and a functionality of about3.5, commercially available from Cognis Corporation.

Hydrophobic Polyol 4 is a slightly branched aliphatic diol having ahydroxyl value of from 117-130 mg KOH/g, and a functionality of about2.2, commercially available from Cognis Corporation.

Hydrophobic Polyol 5 is a branched polyether/polyester polyol having ahydroxyl value of from 300-330 mg KOH/g, and a functionality of about3.0, commercially available from Cognis Corporation.

Hydrophobic Polyol 6 is castor oil, commercially available from EagleSpecialty Products, Inc.

Supplemental Polyol is a trifunctional polyol formed by adding propyleneoxide to a glycerine initiator, having a hydroxyl number of from 388-408mg KOH/g, commercially available from BASF Corporation.

Chain Extender is DPG.

Molecular Sieve 1 is Baylith Paste, commercially available from JACAABL.L.C. of St. Louis, Mo.

Molecular Sieve 2 is Molecular Sieve 3A.

Aminosilane is SILQUEST® A-1100, commercially available from MomentivePerformance Products.

Antifoaming Agent 1 is Antifoam MSA, commercially available from DowCorning.

Antifoaming Agent 2 is Antifoam A, commercially available from DowCorning.

Fumed Silica is AEROSIL® R-972, commercially available from EvonikDegussa.

Isocyanate-prepolymer is a liquid, modified short chain prepolymer basedon pure 4,4′-MDI and having an NCO content of 22.9 wt. %, commerciallyavailable from BASF Corporation.

Polymeric isocyanate is a PMDI with a functionality of about 2.7 and anNCO content of 31.5 wt. %, commercially available from BASF Corporation.

Examples 1-4 are comparative examples and Examples 5 and 6 are inventiveexamples. Example 2 has poor reproducibility. Example 3 is susceptibleto water, causing failure to composite materials formed therefrom.Examples 4, 5 and 6 have excellent hydrophobicity and strengthproperties.

To evaluate physical properties of the composite materials, varioustests are conducted. Crush strength (or compressive strength) isdetermined according to ASTM D 1621. Flexural strength is determinedaccording to ASTM D 790. Flexural modulus is determined according toASTM D 790. Porosity (or void volume) is determined by either of themethods described in: Montes, F., Valavala, S., and Haselbach, L. “A NewTest Method for Porosity Measurements of Portland Cement PerviousConcrete,” J. ASTM Int. 2(1), 2005 and Crouch, L. K., Cates, M., Dotson,V. James, Jr., Honeycutt, Keith B., and Badoe, D. A. “Measuring theEffective Air Void Content of Portland Cement Pervious Pavements,” ASTMJournal of Cement, Concrete, and Aggregates, 25(1), 2003. Permeabilityis determined by either of the methods described in: Montes, F.,Haselbach, L. “Measuring Hydraulic Conductivity in Pervious Concrete,”Env. Eng. Sci. 23(6), 2006 and Schaefer, V., Wang, K., Suleimman, M. andKevern, J. “Mix Design Development for Pervious Concrete in Cold WeatherClimates,” Final Report, Civil Engineering, Iowa State University, 2006.

Results of physical testing of the elastomeric compositions of Examples1-5 are indicated in TABLE III below. The symbol ‘---’ indicates thatthe result was not tested or obtained.

TABLE III Elastomeric Composition Example 1 Example 2 Example 3 Example4 Example 5 Tensile Strength, psi 3,190 — 7,517 871 2,324 Elongation, %20 — 6 92 99 Grave's Tear Strength, ppi 188 — 405 64 365 Durometer ShoreHardness 70 (D) — 68 (D) 74 (A) 54 (D) Tg, ° C. — — 70 24 41

Results of physical testing of the elastomeric composition of Example 6,as well as composite material including the same and aggregate areindicated in TABLE IV below. To form the composite material, 4.2 wt. %of the elastomeric composition is mixed with 95.8 wt. % aggregate, whichin Example 6 below is 100% glass having an average diameter of about ¼inches. The glass is commercially available from Glass Plus Inc. ofTomahawk, Wis. The glass is silylated. In order to make the glasssilylated, the glass is tumbled with an aqueous solution comprising 0.3wt. % SILQUEST® A-1120, which is commercially available from MomentivePerformance Products. To surface treat the glass, 5 parts of the aqueoussolution is tumbled with 100 parts of the glass for about 5 minutes. Theaqueous solution is then drained off and the glass is allowed to dry.The glass, now surface treated (or “silylated”), is used to form thecomposite material. Said another way, the glass now includes one or morefunctional groups imparted by the organofunctional alkoxy silane, i.e.,SILQUEST® A-1120, reacting with the glass. The functional groups, e.g.amine groups, are reactive with isocyanate functional groups of theelastomeric composition. The isocyanate functional groups can be freeisocyanate functional groups after reaction to form the elastomericcomposition, such as in instances of over indexing, or isocyanatefunctional groups imparted by one or more components of the elastomericcomposition itself, e.g. the isocyanate-prepolymer, such that thefunctional groups of the glass become part of the reaction to form theelastomeric composition. The results for Example 6* below, CompositeMaterial, is with surface treated glass as the aggregate.

TABLE IV Elastomeric Composition Example 6 Tensile Strength, psi 2,685Elongation, % 100 Grave's Tear Strength, ppi 426 Durometer ShoreHardness, D 56 Peel Strength, ppi 75 Tg, ° C. 44 Composite MaterialExample 6* Crush Strength, psi 1,550 Flexural Strength, psi 711 FlexuralModulus, psi 84,633 Porosity, % 37.6 Permeability, in/hr 1,650

Composite Materials using both untreated and surface treated glass wereprepared and tested. In TABLE V below, the Composite Material of Example6 comprises untreated glass and the Composite Material of Example 6*uses surface treated glass, as described and illustrated above. Crushstrength of the two examples was also tested after boiling the CompositeMaterials in water for 140 minutes. The physical test results areindicated in TABLE V below. The symbol ‘---’ indicates that the resultwas not tested or obtained.

TABLE V Example 6 Example 6* Composite Example Example (after 140 min.(after 140 min. Material 6 6* in boiling water) in boiling water) CrushStrength, psi 1,050 1,550 175 1,190 Flexural Strength, 468 711 — — psiFlexural Modulus, 104,984 84,633 — — psi

With reference to TABLE V above, it can be appreciated that surfacetreating the glass used to form the inventive composite materials of thepresent invention can have dramatic effects on physical properties, withgreat increases in crush strength (and increased resiliency withextended temperature exposure), and great increases in flexuralstrength. Additional testing is done to confirm findings. FIG. 6 shows adramatic improvement in compressive strength (approximately 40%)achieved by pre-treating the glass with an aminosilane solution. Thermalcycling in high humidity conditions shows little or no loss incompressive strength after 75 cycles between −10° C. and 25° C.

Additional preparations and testing of Example 6* is carried to betterestablish physical properties of the same. These physical properties,and the respective test methods, are shown in TABLE VI below.

TABLE VI Property Value Test Method Density (lbs/ft³) 66 ASTM D-1622Hardness (Instant, Shore “D”) 56 ASTM D-2240 Hardness (Dwell, Shore “D”)45 ASTM D-2240 Tensile Strength (psi) 2500 ASTM D-412 Elongation (% atbreak) 50 ASTM D-412 Tear Strength (pli) 600 ASTM D-624

The elastomeric composition of Examples 6 and 6* provides consistentphysical properties for the composite material over a wide range oftemperatures as shown by the dynamic mechanical analysis (DMA) of thecured elastomeric composition as illustrated in FIG. 7.

It is believed that the composite material can also be used reduce urbanheat island effects. As such, additional formulation and testing oncomposite materials similar to Examples 6 and 6* is carried oututilizing different types of colorants as illustrated below in TABLE VIIwith examples E1-E6.

TABLE VII Pavement SRI El, “Sapphire Blue” 49 E2, “Topaz Brown” 51 E3,“Sedona Red” 53 E4, “Amber Brown” 61 E5, “Jade Green” 62 E6, unpigmented69 New Asphalt 0 Old Asphalt 6 New Concrete 38-52 Old Concrete 19-32

As illustrated in TABLE VII above, all five color variants of thecomposite material, when formed into pavement (E1-E5), have a SolarReflective Index (SRI) substantially greater than 29, as does theunpigmented example (E6). TABLE VII also includes SRI data forconventional pavements formed from asphalt and concrete. As shown,unpigmented and pigmented embodiments of the composite material all haveexcellent SRI values. SRI evaluation is performed in accordance withASTM E 1980.

Another inventive example is created, Example 7, which is chemically thesame as Example 6. However, Example 7 is formed step-wise including astep of forming an intermediate-prepolymer, while Example 6 is formed ina batch fashion excluding the formation of the intermediate-prepolymer.To form Example 7, first, a quasi-prepolymer is prepared by reacting aportion of the Resin Composition (either all or a portion of HydrophobicPolyol 6; or either all or a portion of each of Hydrophobic Polyol 6 andChain Extender) with the Isocyanate Component to form anintermediate-prepolymer. Next, the intermediate-prepolymer is reactedwith the remainder of the Resin Composition to form the ElastomericComposition. Example 7 has a number of advantages over Example 6. Forexample, the intermediate-prepolymer is more compatible with theremainder of the Resin Composition (relative to the Isocyanate and ResinComponents of Example 6) such that mixing is improved.

In addition, the intermediate-prepolymer has better low temperatureproperties compared to the Isocyanate Component, which makes it morerobust for use in various locations. For example, because the reactionbetween the intermediate-prepolymer and the Resin composition generallyhas a lower exotherm relative to the reaction of the Isocyanate andResin Components (i.e., a reaction all at once), it is believed thatelastomeric compositions formed from the intermediate-prepolymer willgenerally have less thermal shrinkage relative to elastomericcompositions not employing the intermediate-prepolymer. Furthermore,because mixing properties are improved via use of theintermediate-prepolymer, it is believed that use of the same shouldallow for improved reaction at lower temperatures relative.

Additional inventive examples are prepared, to further illustrateproperties of the intermediate-prepolymers of the present invention. Oneexample, Example 8, includes a Resin Component comprising 53.99 pbw ofHydrophobic Polyol 6, 4.09 pbw of Chain Extender, 0.029 pbw of MolecularSieve 2, and 0.03 pbw of Antifoaming Agent 2. Example 8 further includesan Isocyanate Component comprising 24.96 pbw of Isocyanate-prepolymerand 16.64 pbw of Polymeric isocyanate. Each of the aforementioned pbwvalues are based on 100 parts by weight of the overall elastomericcomposition, on a pre-reaction basis, before the Resin and IsocyanateComponents are mixed to form Example 8. To form an elastomericcomposition, i.e., Example 8, the Resin and Isocyanate Components aremixed to form a reaction mixture. The reaction mixture is allowed toreact for 20 minutes. After this 20 minute period, aggregate, e.g.glass, is coated with the reaction mixture to form a composite material.The composite material comprises about 4.2 wt. % of the elastomericcomposition and about 95.8 wt. % aggregate. Upon coating of theaggregate, the composite material is immediately introduced into water,e.g. by dumping, such that the composite material is submerged whilecuring to a final cure state. The composite material cured to the finalcure state very well and had little to no evidence of reaction with thewater (based upon visual inspection). The reaction mixture had a freeNCO content of about 22.7% at the 20 minute time described above. Basedon the free NCO content, the point of reaction where little to noreaction with water occurs can be determined. Therefore, an intermediateprepolymer having the same free NCO content is prepared. The point ofreaction can vary based on which materials are employed, however, themethod of determining the proper free NCO content, based on allocatingcertain time intervals prior to introduction of water, works the same.

Inventive Examples 9 and 10 are prepared, both of which areintermediate-prepolymers. Example 9 is prepared as follows: 362.48 g ofPolymeric isocyanate and 543.72 g of Isocyanate-prepolymer are chargedto a 2-L glass flask with agitation to form an Isocyanate Component. TheIsocyanate Component is heated to 60° C. and 93.8 g of HydrophobicPolyol 6 is gradually added, while maintaining the temperature below 80°C. After addition of the Hydrophobic Polyol 6 is complete, the reactionmixture is heated to 80° C. for one hour. The reaction mixture, i.e.,the intermediate prepolymer, is cooled to room temperature thereafter.

Example 10 is prepared as follows: 365.70 g of Polymeric isocyanate and548.55 g of Isocyanate-prepolymer are charged to a 2-L glass flask withagitation to form an Isocyanate Component. The Isocyanate Component isheated to 60° C. and 79.71 g of Hydrophobic Polyol 6 and 6.04 g of ChainExtender are gradually added, while maintaining the temperature below80° C. After addition of the Hydrophobic Polyol 6 and Chain Extender iscomplete, the reaction mixture is heated to 80° C. for one hour. Thereaction mixture, i.e., the intermediate prepolymer, is cooled to roomtemperature thereafter.

To evaluate physical properties of the elastomer compositions (withoutaggregate), upon approaching or reaching a final cure state, varioustests are conducted. Tensile strength and Elongation is determinedaccording to ASTM D 412 or ASTM D 638. Grave's tear strength isdetermined according to ASTM D 624. Durometer Shore D hardness isdetermined according to ASTM D 2240. Peel strength is determinedaccording to ASTM D 6862.

It is to be understood that the appended claims are not limited toexpress and particular compounds, compositions, or methods described inthe detailed description, which may vary between particular embodimentswhich fall within the scope of the appended claims. With respect to anyMarkush groups relied upon herein for describing particular features oraspects of various embodiments, it is to be appreciated that different,special, and/or unexpected results may be obtained from each member ofthe respective Markush group independent from all other Markush members.Each member of a Markush group may be relied upon individually and or incombination and provides adequate support for specific embodimentswithin the scope of the appended claims.

It is also to be understood that any ranges and subranges relied upon indescribing various embodiments of the present invention independentlyand collectively fall within the scope of the appended claims, and areunderstood to describe and contemplate all ranges including whole and/orfractional values therein, even if such values are not expressly writtenherein. One of skill in the art readily recognizes that the enumeratedranges and subranges sufficiently describe and enable variousembodiments of the present invention, and such ranges and subranges maybe further delineated into relevant halves, thirds, quarters, fifths,and so on. As just one example, a range “of from 0.1 to 0.9” may befurther delineated into a lower third, i.e., from 0.1 to 0.3, a middlethird, i.e., from 0.4 to 0.6, and an upper third, i.e., from 0.7 to 0.9,which individually and collectively are within the scope of the appendedclaims, and may be relied upon individually and/or collectively andprovide adequate support for specific embodiments within the scope ofthe appended claims. In addition, with respect to the language whichdefines or modifies a range, such as “at least,” “greater than,” “lessthan,” “no more than,” and the like, it is to be understood that suchlanguage includes subranges and/or an upper or lower limit. As anotherexample, a range of “at least 10” inherently includes a subrange of fromat least 10 to 35, a subrange of from at least 10 to 25, a subrange offrom 25 to 35, and so on, and each subrange may be relied uponindividually and/or collectively and provides adequate support forspecific embodiments within the scope of the appended claims. Finally,an individual number within a disclosed range may be relied upon andprovides adequate support for specific embodiments within the scope ofthe appended claims. For example, a range “of from 1 to 9” includesvarious individual integers, such as 3, as well as individual numbersincluding a decimal point (or fraction), such as 4.1, which may berelied upon and provide adequate support for specific embodiments withinthe scope of the appended claims.

The present invention has been described herein in an illustrativemanner, and it is to be understood that the terminology which has beenused is intended to be in the nature of words of description rather thanof limitation. Many modifications and variations of the presentinvention are possible in light of the above teachings. The inventionmay be practiced otherwise than as specifically described within thescope of the appended claims.

What is claimed is:
 1. A composite pavement structure comprising: awearing course layer comprising aggregate and an elastomeric compositioncomprising the reaction product of; an isocyanate component comprising apolymeric isocyanate, and optionally, an isocyanate-prepolymer, and anisocyanate-reactive component comprising a hydrophobic polyol, and achain extender having at least two hydroxyl groups and a molecularweight of from about 62 to about 220; and a base course layer disposedbelow said wearing course layer, said base course layer comprisingaggregate the same as or different than said aggregate of said wearingcourse layer; wherein said aggregate of said wearing course layercomprises from about 1 to 100 wt. % glass.
 2. A composite pavementstructure as set forth in claim 1 wherein said aggregate of said basecourse layer is unbound, whereas said aggregate of said wearing courselayer is bound by said elastomeric composition.
 3. A composite pavementstructure as set forth in claim 2 wherein both of said wearing and basecourse layers are porous.
 4. A composite pavement structure as set forthin claim 1 wherein said aggregate of said base course layer comprisesglass or rock.
 5. A composite pavement structure as set forth in claim 1wherein said glass includes a surface treatment comprising at least oneamine and/or amino functional group reactive with an isocyanatefunctional group of said elastomeric composition.
 6. A compositepavement structure as set forth in claim 1 wherein said glass has anaverage diameter of from about 0.1 to about 1.0 inches.
 7. A compositepavement structure as set forth in claim 1 wherein said wearing courselayer has an average thickness of from about 1 to about 5 inches, andsaid base course layer has an average thickness of from about 2 to about12 inches.
 8. A composite pavement structure as set forth in claim 1further comprising a choker course layer sandwiched between said wearingand base course layers, said choker course layer comprising aggregateand being different than said wearing and base course layers and havingan average thickness of from about 0.5 to about 2.5 inches.
 9. Acomposite pavement structure as set forth in claim 1 further comprisinga geosynthetic layer disposed under said wearing course layer andwherein said geosynthetic layer comprises a geotextile.
 10. A compositepavement structure as set forth in claim 1 further comprising a surfaceovercoat disposed on a surface of said wearing course layer oppositesaid base course layer and wherein said surface overcoat is formed froma UV stable polyurethane elastomer.
 11. A composite pavement structureas set forth in claim 1 wherein: i) said isocyanate component comprisessaid polymeric isocyanate and said isocyanate-prepolymer and saidisocyanate-prepolymer is present in said isocyanate component in anamount of from about 25 to about 75 parts by weight based on 100 partsby weight of said isocyanate component; and/or ii) said chain extenderis present in said isocyanate-reactive component in an amount of fromabout 5 to about 10 parts by weight based on 100 parts by weight of saidisocyanate-reactive component.
 12. A composite pavement structure as setforth in claim 1 wherein said hydrophobic polyol comprises a natural oilpolyol and wherein said natural oil polyol is castor oil.
 13. Acomposite pavement structure as set forth in claim 1 wherein said chainextender comprises an alkylene glycol and wherein said alkylene glycolis dipropylene glycol.
 14. A composite pavement structure as set forthin claim 1 wherein said isocyanate-prepolymer comprises the reactionproduct of a diphenylmethane diisocyanate and a polyol, has an NCOcontent of about 22.9 wt. %, and an average NCO functionality of fromabout 2 to about
 3. 15. A composite pavement structure as set forth inclaim 1 wherein said polymeric isocyanate comprises polymericdiphenylmethane diisocyanate, has an NCO content of about 31.5 wt. %,and an average NCO functionality of from about 2 to about
 3. 16. Acomposite pavement structure as set forth in claim 1 wherein: i) saidhydrophobic polyol is present in said isocyanate-reactive component inan amount of from about 80 to about 99 parts by weight based on 100parts by weight of said isocyanate-reactive component; and/or ii) saidelastomeric composition is present in said wearing course layer in anamount of from about 1 to about 10 parts by weight based on 100 parts byweight of said wearing course layer.
 17. A composite pavement structureas set forth in claim 1 free of a supplemental support structure.
 18. Acomposite pavement structure comprising: a wearing course layercomprising aggregate and an elastomeric composition, said elastomericcomposition comprising the reaction product of; an isocyanate componentcomprising a polymeric isocyanate, and optionally, anisocyanate-prepolymer, and an isocyanate-reactive component comprising ahydrophobic polyol, and a chain extender having at least two hydroxylgroups and a molecular weight of from about 62 to about 220; a basecourse layer disposed below said wearing course layer, said base courselayer comprising aggregate the same as or different than said aggregateof said wearing course layer; a choker course layer sandwiched betweensaid wearing and base course layers; a geotextile layer disposed undersaid choker course layer and/or said base course layer; and optionally,a surface overcoat disposed on a surface of said wearing course layeropposite said base course layer; wherein said aggregate of said wearingcourse layer comprises from about 1 to 100 wt. % glass and having anaverage diameter of about 0.25 inches or less, said aggregate of saidbase course layer comprises rock or glass and has an average diameter offrom about 0.375 to about 0.75 inches, and said aggregate of said chokercourse layer has an average diameter of from about 0.25 to about 0.375inches; and wherein said wearing course layer has an average thicknessof from about 2.5 to about 3.5 inches, said choker course layer has anaverage thickness of about 1.5 inches, said base course layer has anaverage thickness of from about 4 to about 8 inches, and said surfaceovercoat has an average thickness of about 5 mils or greater.
 19. Acomposite pavement structure as set forth in claim 18 wherein said glassincludes a surface treatment comprising at least one amine and/or aminofunctional group reactive with an isocyanate group of said elastomericcomposition.
 20. A composite pavement structure as set forth in claim 18wherein said wearing, choker and base course layers are all porous. 21.A method of paving an area defining a cavity with a composite pavementstructure, wherein the composite pavement structure is as set forth inclaim 1, said method comprising the steps of: optionally, disposing ageosynthetic into the cavity; disposing aggregate into the cavity toform the base course layer; optionally, disposing aggregate into thecavity to form a choker course layer; coating aggregate with theelastomeric composition of the wearing course layer to form a compositematerial; disposing the composite material into the cavity to form thewearing course layer within the area; optionally, positioning formsabout a perimeter of the area; optionally, screeding the compositematerial; optionally, compacting the composite material to reduceporosity of the wearing course layer; and optionally, finishing asurface of the wearing course layer to orient the aggregate of thesurface into a planar relationship with each other and impart thesurface with a flat profile in cross-section to resist spalling of thewearing course layer.
 22. A method of paving as set forth in claim 21further comprising the step of applying an overcoat to the surface ofthe wearing course layer after the step of finishing.
 23. A method asset forth in claim 21 wherein: i) the step of screeding the compositematerial is further defined as leveling the composite material with apower screeder; and/or ii) the step of finishing the surface of thewearing course layer is further defined as manipulating a finishing toolalong the surface to finish the surface of the wearing course layer andwherein the finishing tool is a power trowel or a fresco blade.